Bags which can be filled with a dry charge by means of a bag-filling machine have been known for a long time. The charge is intended to be mixed with moist materials at a site of use in order, in this manner, to obtain a hardening compound, for example concrete. To this end, the bag, formed as a valve bag, is cut open at its top end and the dry charge that gives off dust is poured into a mixing device in which it is processed to form a moist mixture, which hardens when the mixing operation is concluded. An example of such a charge is cement which is processed in a concrete mixing machine or concrete mixing plant with water, sand and where applicable gravel to form a slightly moist mortar mixture which is castable on site, generally speaking on a building site, into a formwork and hardens there in order to form, for example, a concrete support, a concrete wall or the like.
Pouring the dry and dusty charge into the mixing device in this case causes problems because part of the charge presents as dust. This is unpleasant for the operator not only on account of the dirt linked thereto but also because it is also potentially hazardous to health.
Consequently, the idea arose to design a bag of this type with a bag wall that dissolves in a moist environment so that the bag with the charge can be thrown into the mixing device unopened. Once the bag wall has dissolved, the charge is available as the required cement in order to produce the mortar mixture. In so far as the bag wall, which is formed from water-soluble paper, dissolves completely, the (paper) material of the wall is not detrimental to the forming of the concrete. The opening of the bag and the pouring out of the charge into the mixing device leading inevitably to the charge presenting as dust could, consequently, be avoided with this method.
However, it has been shown that with normal mixing times of a few minutes, it is not possible to achieve complete dissolution of the bag wall, but rather pieces of bag wall of not insignificant size remain in the mixture. This is unacceptable as the remaining pieces from the material of the bag wall, that is to say in particular pieces of paper, impede the stable concrete bond and thus cause weak points in the concrete component. Consequently, a solution that is acceptable in practice for a bag that dissolves completely in a moist environment within a mixing device has not yet been found.